Search found 160 matches

by jmc2000
Mon Oct 17, 2016 12:15 am
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

mfb wrote:They made a high pileup test yesterday. Bunch trains with ~50 collisions per interaction, and a few individual bunches with 90-95 collisions. That is about 4 times the design value, and not far away from the HL-LHC conditions (140, maybe up to 200).
Has anything been published about this?

JMc
by jmc2000
Mon Sep 26, 2016 4:14 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

Record luminosities for Atlas: 13.75 Hz/nb, CMS: 14.5 Hz/nb !! The latest LHCC meeting makes for interesting reading: https://indico.cern.ch/event/563488/ page 14: https://indico.cern.ch/event/563488/contributions/2277292/attachments/1340292/2019570/20160921_LHCC.pdf "~40-45 fb-1/year in 2017 and 20...
by jmc2000
Sat Sep 03, 2016 9:06 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

New record for instantaneous luminosity for CMS at ~13.5 hz/nb ! and it's back to averaging 2.5\fb/week as in early August. But it's difficult to know how much out of calibration CMS is, and whether the record is real. Fingers crossed, >35\fb for 2016 is looking realistic which is x3 the data presen...
by jmc2000
Wed Aug 10, 2016 5:59 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

It is an electric problem - the beam drilling a hole through the magnet would look differently. A short on the winding of a dipole magnet will mean it being warmed up to room temperature, replaced, then recooled as with a drilled example - 30 days repair with most of the days needed for the warming...
by jmc2000
Wed Aug 10, 2016 4:07 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

Suspected short on dipole 31L2 which could be bad news in taking 30 days to replace: http://www.symmetrymagazine.org/article/december-2007/protecting-the-lhc-from-itself “In a bad accident, the beam could go off course and drill a hole through one or two magnets,” says Schmidt. While this would not ...
by jmc2000
Mon Aug 08, 2016 1:07 am
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

Recorded integrated luminosity/week ~1.6fb compared to ~2.5fb before the MDs which still looks pretty good, considering that there was even talk of replacing magnet D that would have taken 8 days, plus a few hundred hours of intensity ramp up. I wonder how much of the recent MD will be used over the...
by jmc2000
Sat Aug 06, 2016 11:12 pm
Forum: The Accelerator
Topic: CMS and ATLAS luminosity: are they jealous?
Replies: 6
Views: 16165

Re: CMS and ATLAS luminosity: are they jealous?

Does anyone know why the CMS luminosity is 10% larger than ATLAS, despite being the same before the MDs?

JMc
by jmc2000
Thu Jul 28, 2016 9:17 pm
Forum: The Accelerator
Topic: Which page holds the correct luminosity results?
Replies: 1
Views: 9095

Which page holds the correct luminosity results?

There's a difference between the luminosity results for ATLAS and CMS recorded on the main coordination page: [/url]https://acc-stats.web.cern.ch/acc-stats/#lhc/[url] And on the CMS ATLAS sites: [url]https://twiki.cern.ch/twiki/bin/view/CMSPublic/LumiPublicResults[url] [url]https://twiki.cern.ch/twi...
by jmc2000
Sun Jul 24, 2016 7:47 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

The BCMS scheme now reliably delivers 120% design luminosity. Also a noticeable improvement in initial beam life time from 5 to 7 hours, giving an incredible 100\fb over just 2.5 hours. Fingers crossed they may even take it to 130%, but the current problem with cryogenics might be a sign of this be...
by jmc2000
Sun Jul 24, 2016 7:11 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

https://lpc.web.cern.ch/lumiplots_2016_pp.htm Is this what you mean? There is also the statistics page which is linked on the portal. Something more like this: https://op-webtools.web.cern.ch/vistar/vistars.php?usr=LHC3 But a luminosity plot for a particular fill rather than over the last 24 hours....
by jmc2000
Sun Jul 24, 2016 12:57 am
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

The luminosity lifetime might go down a bit, but for a given time in stable beams the luminosity should always be higher, so no disadvantages (higher pileup in the experiments, but that's what you get if you want more luminosity for a given number of bunch crossings). Just challenging for the preac...
by jmc2000
Thu Jul 21, 2016 12:02 am
Forum: The Accelerator
Topic: 2016 Machine Development
Replies: 1
Views: 9649

2016 Machine Development

Is there any information on the type of machine development that is planned for 2016, how it's hoped to improve operation of the LHC?

JMc
by jmc2000
Mon Jul 18, 2016 1:58 am
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

What's going on when there is a sudden increase in luminosity during stable beams, as shown here with Atlas at t=2:50 https://www.flickr.com/photos/48562472@ ... res/W4K8nQ

JMc
by jmc2000
Sat Jul 09, 2016 3:18 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

https://lpc.web.cern.ch/lpc-minutes/2016-06-27.htm This seems like they are not planning on fixing the SPS beam dump system this year. There's an interesting paper on BCMS mentioned in the link which is now being used for fills as we speak to increase the luminosity further: http://emetral.web.cern...
by jmc2000
Thu Jul 07, 2016 6:27 pm
Forum: The Accelerator
Topic: 2016 operation
Replies: 52
Views: 88882

Re: 2016 operation

They plan to reduce the emittance a bit, which could increase the luminosity further even without a fix of the SPS issue. What are the disadvantages to reducing the emittance? I remember in 2012 that the beam half life was severely reduced from 20 hours to around 8 hours as the luminosity was incre...